1. Field of the Invention
The present invention relates to two-component adhesive, sealant, and coating compositions and particularly to two-component compositions containing silylated polyurethanes.
2. Background Art
Adhesives are commonly used to join or fasten two or more adherends. Adherends are considered as being any two or more materials, or pieces of material that are being joined together, including wood, metals, plastics, paper, ceramics, stone, glass, concrete, etc. Adhesives used for these purposes are based on a wide range of technologies, including elastomer/solvent/resin mixtures, epoxies, latexes, polyurethanes, silicones, cyanoacrylates, acrylics, hot melts, and others. Such adhesives can have one or more drawbacks, such as they may contain solvents which are toxic and often flammable, they can be incompatible with one or more classes of adherends, they can have undesirably long cure times and in many cases the bonds they form are of insufficient strength.
It is often desirable for coatings applied to substrates to provide a desirable appearance, in many cases by applying multiple coating layers, the last of which can be a pigmented or unpigmented topcoat. Unfortunately, as the article containing the coated substrate ages, scratches that occur through normal “wear and tear”, tend to deteriorate the appearance of the coated surface of the substrate,
A sealant is typically a thin film, often containing a plastic, that is applied onto one or more surfaces on one or more substrates to prevent passage of a liquid or gas through the film. The sealant can be used to prevent exposure of the substrate or is often additionally used to prevent exposure via defects in a substrate or between gaps that can exist between substrates.
Silane functional resins are typically cured or crosslinked in a two-step sequence that requires first a reaction of water with an alkoxysilane group to form a silanol group followed by reaction of the silanol group with either another silanol group or an alkoxy silane. In one-component silane formulations, catalysts are typically included in order to increase the speed of the reactions. In many cases, the absorption of water is a limiting step in the curing or crosslinking process.
U.S. Pat. No. 5,936,032 to Angus, Jr. discloses a two part room temperature vulcanizable silicone adhesive sealant composition consisting of components A and B. Component A includes an alkoxy endcapped polydiorganosiloxane, a condensation curing catalyst, and a polyalkoxysilane crosslinking agent. Component B includes water and a disilanol endstopped polydiorganosiloxane.
U.S. Pat. Nos. 4,386,992 and 4,479,840 to Takegawa, et al. disclose a two-part adhesive that includes an aqueous synthetic resin emulsion adhesive and a gelling agent including a combination of a calcium salt, which can be calcium aspartate and an organic acid salt or an inorganic acid salt.
U.S. Pat. No. 6,649,016 to Wu et al. discloses an adhesive composition useful for bonding glass to a painted substrate that includes one or more polymers having a flexible backbone and silane moieties capable of silanol condensation; one or more titanates or zirconates; and an anhydrous strong organic acid.
U.S. Published Application 20030055197 A1 to Morikawa et al. discloses a laminate adhesive that includes a polyisocyanate curing agent containing an isocyanate group-terminated prepolymer and a silane coupling agent and an active hydrogen group-containing resin.
U.S. Pat. No. 6,114,436 to Roesler discloses moisture-curable compositions containing polyisocyanates having (cyclo)aliphatically-bound isocyanate groups and compounds containing alkoxysilane groups. The moisture-curable compositions can be used in coatings, adhesives or sealants.
U.S. Pat. No. 6,096,823 to Shaffer discloses moisture-curable compounds which have an isocyanate group content and an alkoxysilane group content and optionally contain repeating ethylene oxide units. The alkoxysilane groups are incorporated as the reaction products of a polyisocyanate component and amino compounds containing alkoxysilane groups. The moisture-curable compounds are useful in adhesive or sealing compositions as a binder.
U.S. Pat. No. 5,554,709 to Emmerling et al. discloses moisture-curing alkoxysilane-terminated polyurethanes obtained by reacting polyurethane prepolymers with sulfur-free alkoxysilanes. The moisture-curing alkoxysilane-terminated polyurethanes can be used in sealing and/or adhesive compositions.
However, known adhesives, sealants and coatings utilizing silane functional resins suffer from having a poor or short shelf life and/or stability and/or are slow to cure. Therefore, it would be desirable to identify adhesives containing silane functional resins that have a good or long shelf life and a reasonably fast rate of cure or crosslinking.